U.S. President Barack Obama is demanding "concrete proposals" on curbing gun violence that he could send to Congress no later than January — an urgent effort to build on the growing political consensus over gun restrictions following last week's massacre of children at a Connecticut school.

It was a tough new tone for the president on Wednesday, whose first four years were largely quiet on the issue amid widespread political reluctance to tackle a powerful gun-rights lobby.

'This time, the words need to lead to action.'—U.S. President Barack Obama

But emotions have been high after the gunman in Friday's shooting used a semi-automatic rifle to kill 20 young children and six adults at the school, shooting many several times and at close range, after killing his mother at home. He then killed himself.

"This time, the words need to lead to action," Obama said. He said he will push legislation "without delay" and urged Congress to hold votes on the bill next year.

"The fact that this problem is complex can no longer be an excuse for doing nothing," Obama said. "The fact that we can't prevent every act of violence doesn't mean we can't steadily reduce the violence."

Tom Mauser, who became a gun control lobbyist after his 15-year-old son Daniel died in the 1999 Columbine high school shooting in Colorado, told CBC News he believes Obama will act on his words.

Tom Mauser, father of Daniel Mauser who was killed in the 1999 Columbine school shooting, said the Newtown, Conn., shooting has been 'a tipping point for many people.' (Chris Schneider/Associated Press)

After previous school shootings, he said, the culture in America has been to forget, with Americans moving on and accepting this kind of violence.

Mauser said he doesn't think history will repeat itself this time.

"A lot of people are upset. I think this has really been a tipping point for many people," he said. "We can't just accept the status quo."

As part of Obama's call for "real progress, right now," he pressed Congress to reinstate an assault weapon ban, which expired in 2004. He also called for stricter background checks for people who seek to purchase weapons and limited high-capacity magazines.

Vice-President Joe Biden, a longtime gun control advocate with decades of experience in the Senate, will lead a team that will include members of Obama's administration and outside groups.

Funerals continue

In the days since the shooting, Obama has vowed to use "whatever power this office holds" to safeguard the nation's children after Friday's shooting. Funerals for the victims continued Wednesday, along with the wake for the school's beloved principal.

The shooting has prompted several congressional gun-rights supporters to consider new legislation to control firearms, and there are concerns in the administration and elsewhere that their willingness to engage could fade as the shock and sorrow over the shooting eases.

A mourner carries a program as she leaves the funeral service of Victoria Soto on Wednesday in Stratford, Conn. Soto, a teacher, died in the Dec. 14 massacre at Sandy Hook Elementary School. (Jason DeCrow/Associated Press)

The most powerful supporter of gun owners and the gun industry, the National Rifle Association, broke its silence Tuesday, four days after the shooting. In a statement, it pledged "to help to make sure this never happens again" and has scheduled a news conference for Friday.

Obama challenged the NRA to join the broader effort to reduce gun violence, saying, "Hopefully they'll do some self-reflection."

With the NRA promising "meaningful contributions" and Obama vowing "meaningful action," the challenge in Washington is to turn words into action. Ideas so far have ranged from banning people from buying more than one gun a month to arming teachers.

The challenge will be striking the right balance with protecting the Second Amendment right to bear arms. Firearms are in a third or more of U.S. households, and suspicion runs deep of an overbearing government whenever it proposes expanding federal authority.

As the gun control debate continues, firearms enthusiasts are stocking up on assault rifles in anticipation of tighter gun control measures:

Colorado set a single-day record for gun background check requests Saturday, the day after the Connecticut massacre.

Nevada saw more requests for background checks in the days after the shooting than any other weekend this year.

Some online retailers are removing assault rifles from websites, partially because of diminishing supplies.

Some gun shop owners are even holding back on sales, anticipating more interest and value after Obama's comments.

At least three companies that make armoured backpacks designed to shield children caught in a shooting are reporting a large spike in sales and interest. The body armour inserts fit into the back panel of a child's backpack and is designed to stop bullets from handguns, not assault rifles.

They sell for about $150 US to $300, depending on the company.

Mental health issues

Many pro-gun lawmakers also have called for a greater focus on mental health issues and the effect of violent entertainment like video games. Obama also prefers a holistic approach, with aides saying stricter gun laws alone are not the answer.

National Guard may boost school safety

Senator Barbara Boxer, a Democrat, is proposing to give schools more money for security improvements and to make greater use of the National Guard.

Boxer's legislation "will help state and local officials protect our children by utilizing all of the law enforcement tools at our disposal," she said in a press release.

The legislation would boost a grants program, which pays for things like metal detectors, from $30 million US annually to $50 million.

A second Boxer bill would give governors financial incentive to use National Guard members in schools, by having the federal government reimburse states for the expense.

Obama said Wednesday that the U.S. needs to make access to mental health care as easy as access to a gun.

Still, much of the immediate focus is on gun control, an issue that has been dormant in Washington for years despite several mass shootings.

Pressure for change has come from several sources this week:

Shares in publicly traded gun manufacturers dropped.

Freedom Group International, the largest firearms maker in the U.S., said Tuesday it was being put up for sale by its owner, private equity group Cerberus Capital Management

Proposed legislation in California would increase the restrictions on purchasing ammunition by requiring buyers to get a permit, undergo a background check and pay a fee.

The U.S. Conference of Mayors wrote Obama and Congress calling for "stronger gun laws, a reversal of the culture of violence in this country, a commission to examine violence in the nation, and more adequate funding for the mental health system."